Dyeing process



United States Patent Great Britain No Drawing. Filed Dec. 26, 1961, Ser.No. 162,248 Claims priority, application Great Britain, Dec. 28, 1960,44,463/60; Jan. 12, 1961, 1,410/61 3 Claims. (Cl. 855) This inventionrelates to a novel process for dyeing synthetic polymer filaments andfibers made e.g. from polyesters, copolyesters, polyamides andpolyolefins.

Commercially available polyester filaments and fibres which are in theirdrawn condition are ditficult to dye and many processes are used toovercome these difiiculties. Thus it has been proposed to melt spinfilaments, which are obtained from a polyester already coloured orpigmented in the melt. This process is now used, on a large scale, forthe manufacture of filaments and fibres coloured white or black. It hasthe disadvantage that, for economic reasons, large batches of fibres orfilaments have to be produced and therefore the range of colours whichcan be made commercially available must be limited.

It is usually preferred to colour fibres by application of dyestuffs.The best known type used for polyester fibres and filaments are dispersedyes, also known as acetate dyes. These are sold in finely divided form,together with a dispersing agent, and they are applied to the fibres, incommercial practice, from aqueous dispersions assisted by dyeingassistants, dye carriers or elevated temperatures at superatmosphericpressure. The disperse acetate dyes can also be applied to polyamide andpolyolefin fibres.

It is well known in the art that the strength of the filaments andfibres made from polyesters, polyamides and polyolefins can beconsiderably increased by a process, in which melt spun filaments areelongated to between 3 and 8 times their original length. Indeed, allsuch fibres and filaments have to be strengthened by a drawing process.During this process the polymer molecules in the filaments or fibresbecome oriented and more closely packed, so that access by othermolecules e.g. dyestuff molecules becomes more difficult and in the caseof polyesters, much more difficult. Dyeing porcesses suggested hithertohave been intended to apply to fully drawn filaments and fibres, usuallyin yarn, tops or fabric form and commercially these processes have beencarried out on such fully drawn material using high temperatures.Suggestions of dyeing undrawn melt spun material have not lead tosuccessful exploitation because of accompanying changes in the filamentsduring the dyeing operation which render the filaments undrawable.

We now provide a process in which a novel colouring process isintegrated into this necessary drawing process, so that both colouringand strengthening of the filaments or fibres can be performed in onecontinuous operation, and advantage can be taken of the permeability ofthe filaments or fibres in their undrawn condition.

This is a process which can be operated by the polyester yarn and fibremanufacturer because of its speed, effectiveness and relative ease ofcontrol.

According to our invention, we provide a rapid, continuous, integratedprocess for the colouration of filaments melt spun from synthetic linearpolymers, comprising applying a dye, as hereinafter defined, dissolved,without dispersing agents or other diluents, in an organic substantiallynon-aqueous hot solvent to undrawn melt spun filaments having abirefringence of less than 3,241,905 Patented Mar. 22, 1966 10 10derived from synthetic linear polymers, as hereinafter defined, underconditions such that penetration of the dye into the filaments is 60% ofthe cross-sectional area, or more, followed by drawing the filamentsthree to six times their length. The dye may be applied at temperaturesup to 150 C. for a very short time, preferably less than 30 secondsusing an organic solvent which dissolves the dye but does not causeembrittlement of the filaments or fibres in their undrawn condition. Thedye must be free from any kind of harmful diluents, soluble in theorganic solvent and substantive to the fibre.

We fined that in the actual dyeing operation, the distribution of dyebetween solvent and fibre obeys the Distribution Law (Glasstone,Textbook of Physical Chemistry, Second Edition p. 736). Whilst it isWell known that this Law applies to the dyeing of fully drawn polyesterfibres with disperse acetate dyes from aqueous dispersions (Vickerstaif,The Physical Chemistry of Dyeing), its application to undrawn yarn in asolvent dyeing system has not previously been disclosed. Thus in thisdyeing system Concentration of dye in the fibre for immersion timesgreater than five seconds. At less than five seconds immersion thepenetration of dye into the fibre is not complete and the dyeing systemhas not reached practical equilibrium.

Heavy shades of colour on synthetic polymer filaments are produced whenthe concentration of dye in the fibre is about 2% or more. Therefore, toobtain a full range of shades or colour up to heavy shades, in oursolvent dyeing system, about 2% or more of dye should be dyed onto thefibre. Thus in Equation 1, the concentration of dye in the fibre mustequal or be greater than 2% i.e. C 22 and hence the combinations of dyesand solvents which can be used are defined by the conditions KC ZZ.

The system works best when the dye is in true solution in the solvent,so that C should not exceed the saturation solubility of the dye in thesolvent at the temperature of dyeing. Thus Sat.

The condition for choosing dyes and solvents then becomes KC ZZ (2)Dyes, of course, should be choosen from those dyes which are substantive(i.e. fixed and permanent) to the fibre being dyed. For polyester fibresand filaments these are usually in the class of dyes called the disperseacetate dyes. Solvents must be chosen from those which are suflicientlygood solvents of the chosen dye to satisfy Equation 2 and which alsohave no adverse effect on any of the properties of the dyed, drawnfibre. For a cornmercial process, solvents of low volatility,inflammability and tenacity are preferred. Solubility in water is anadvantage in that water can be used to wash olf solvent and unuseddyestutf from the treated, dyed, undrawn or drawn fibre or filaments.

We find that high boiling organic liquids such as ethylene glycol,diethylene glycol, polyglycols and ethylene oxide condensates of averagemolecular weight of up to 6000, preferably between 200 and 1000, theiresters and ethers and mixtures thereof, dirnethyl and diethyl sebaca-te,oleic acid, mesitylene, triphenyl phosphate, and glycerol are allsuitable solvents and work best in the region between and C., thefilaments being in contact with the dye solution for a time less than 30seconds,

preferably between 5 and 15 seconds. Lower boiling solvents such astrichlorethylene, carbon tetrachloride, acetone, benzene and glacialacetic acid, are also suitable and work best at or near their boilingpoints. Because of the higher volatility of these solvents it isnecessary to fit the dye bath with means for condensing and returning tothe bath vapours from the boiling solvents. Immersion times of up to 30seconds, preferably between 5 and 15 seconds are again required.

Preferred solvents for use in our process are in the series fromethylene glycol, through diethylene glycol to polyethylene glycol of upto 1000 average molecular weight and from these we select ethyleneglycol as the best solvent for use with polyester fibres. It will beappreciated that mixtures of these solvents may be used which arecompatible with each other and which are liquid under treatingconditions. The coefficient K in Formula 2 is preferably 0.2-1.6.

The shades of colour which can be obtained by our process can be variedby altering the temperature of the dyestuff solution, or by increasingthe concentration of the dyestufi" in the solvent, but below saturationlevel. We find moreover that the dyestuff penetrates the spun undrawnyarn very rapidly, so that after 5 seconds immersion, only smallimprovements in shade can be obtained by increasing the immersion time.Because of this rapid penetration into the undrawn yarn, it is possible,if so desired, to remove excess dyestuff solution before the drawingstage of the process, without any deleterious effect on the colour ofthe drawn yarn.

We have found, however, that a number of organic liquids, whilst beingexcellent solvents for dyestuffs and being very suitable fortransferring dyestuff into the undrawn fibre, have an effect on theundrawn polyester fibre whereby it is embrittled and rendered difficultor impossible to draw, after colouring. Such solvents are cyclohexanone,cinnamaldehyde, benzyl alcohol and chloroform. These solvents are allknown to diffuse rapidly into polyesters but they affect thecrystallinity of the material.

With polyamide and polyolefin fibres this effect was also apparent whensolvents known to penetrate the fibres easily, were used.

Undrawn fibres and filaments from copolyesters such as polyethylenesebacate/terephthalate containing up to 15 moles percent of sebacatecomponent, can also be treated and we find that they give improvedshades of colour when treated according to our invention.

Colours can be chosen from classes of dyestuffs, such as disperseacetate dyes and optical whiteners (e.g. UVITEX R.T.M.) theunsulphonated bases of acid wool dyes, or from pigments, such as the oilsoluble pigments and the vat pigments. However, with regard to theconditions already defined for choosing colours for use in our process,disperse acetate dyes are the most substantive towards polyesterfilaments.

In applying our process to the continuous dyeing of undrawn filaments,that is to filaments with a birefringence less than 10- it iscommercial-1y advantageous to treat a large number of filaments at thesame time, in the form of a tow. Because such tows have a highmechanical pick-up of liquid, it is necessary to restrict the pick-up ofliquid from the solvent dye bath by manglin g the tow as it leaves thedye bath so that the pick-up of solution is reduced from about 150% toabout 10%. The pick-up is defined here as the weight of the liquidpresent on a given length of the wet tow divided by the weight of thesame piece of tow when dry. Alternatively and preferably, the solutionof dyestuff can be applied to the tow of undrawn filaments by apad-mangling system so that the amount of dye solution applied iscontrolled to a pick-up of 2535%. The wet tow must then be maintained atthe temperature required for dyeing and for the required time forexample in a hot air furn ve, r by sliding conta t with a h t pla e orin a radiative furnace until penetration of the dye into the filamentsis 60% or more.

A suitable apparatus for dyeing filament tows with a pad-mangling systemand a draw frame for drawing the filaments comprises two resilient e.g.rubber covered rolls, one fixed to a shaft driven e.g. by a gear boxdrive from the feed rolls of the subsequent draw furnace and the otherrunning on a floating shaft which can be loaded to press the rolls andthe filaments between the rolls together, by a controlled amount, meansfor feeding and maintaining dye solution in a padding bath between thenip of the resilient rolls at a constant level and means for maintainingthe bath at a constant temperature, such as side plates containing theresilient rolls with low voltage electric thermostatic or controllablecartridge heaters, which float freely on the rolls, a feed pipe for thedye solution and an overflow return pipe in the side plates formaintaining the padding bath at a constant level and temperature; on thedraw frame feed rolls driven at the same surface speed as the resilientrolls of the pad-mangling system and draw rolls 38 times faster than thefeed rolls with means for heating the filaments just before or on thedraw frame. The simplest form of heating means is a hot water bathbetween the feed and draw rolls, but if desired alternatively orsimultaneously the feed and/or the draw rolls may be heated, or anyother known suitable heating means may be used during drawing. Dyesolution which has not penetrated into the filaments may be removedbefore, during or after drawing by circulating liquid baths or bysprays. If the filaments become wet during drawing i.e. if dry heatingmeans are not used during drawing, it is necessary to complete thedyeing treatment before drawing. A suitable heating device comprises athermostatically controlled heater tube mounted vertically below thepad-mangle. A heater tube 1 m. long has been found suitable in which thetemperature is maintained as in the pad-mangle. Between the rolls andthe heater tube is a drip tray to collect any drips or splashes of thedye solution. A solvent, e.g. glycol, drip feed may be introduced at thetop of the tube to keep the tube-atmosphere saturated with solvent, e.g.glycol, vapour without directly contacting the filaments. The undrawntow of filaments passes into the pad-mangling system where it picks up25-30% of a solution of dye in solvent at a temperature appropriate tothe solvent, passes out of the nip of the mangle directly into theheater tube, the whole tow running at a speed such that there is a dwelltime of between 5 and 30 seconds in the hot zone, thereby substantiallycompleting the dye treatment. The dyed undrawn tow then passes directlyonto a set of feed rolls, through a drawing zone and onto a similar setof drawing rolls rotating at between 3 and 6 times the speed of the feedrolls in the case of polyester and polyamide filaments and up to eighttimes in the case of polypropylene filaments. The dyed, drawn yarn maythen be washed free of solvent and unused dyestuff by water sprays or bya circulating water bath, crimped, dried, heat set to reduce theresidual shrinkage to one percent or less in boiling water for oneminute and, if desired, cut into staple fibres.

The following examples illustrate, but do not limit our invention inwhich parts and percentages are by weight, as applicable.

EXAMPLE 1 Melt spun undrawn polyethylene terephthalate filaments in theform of 2000 denier about 200 filament tow is continuously immersed bypassage through a dyebath solution containing 1 part of dye C.I. (ColourIndex) No. 62015 in 99 parts of ethylene glycol, heated to C. at aboutfeet/min, under conditions such that the dwell time in the dyebath is 5seconds. The dye concentration and dyebath level are maintained toobtain a uniform colour on the filaments. The dyed tow is thencontinuously taken up by feed rolls of a draw frame Where the filamentsare elongated 3.6 times their length in steam at 95-100 C. The tow isthen passed over a series of rolls and sprayed with hot water at 60-70C. to continuously remove excess dye and solvent. The still wet tow ispassed to a stuffer box crimper and crimped, dried and the crimped towis heat-set at 140 C. in a relaxed condition, whereby the residualshrinkage in boiling water is reduced to less than 1% A crimped tow offilaments of an excellent shade of mauve-red is obtained. Thebirefringence of the undrawn uncoloured filaments is 0.005 and of thedrawn filaments 0.21. The tow is cut into staple fibres which are mauvered and which shrink less than 1% in boiling water EXAMPLE 2 A solutionof five parts of dyestuif, C.I. (Colour Index) No. 62015.

O NHn in 95 parts of ethylene glycol, used under the same conditions asExample 1, produces a very heavy red shade on the finished filaments,which when cut into staple fibre lengths shrink less than 1% in boilingwater.

EXAMPLE 3 A solution of two parts of the pigment, C.I. No. 60725 t Y O IOH O in 98 parts of polyethylene glycol (molecular weight 600) used asin Example 1 produces a heavy shade of blue on the finished tow. Fibrescut from the crimped filaments when made up into fabrics do not pill andshrink less than 1% in boiling water.

It should be appreciated that by means of our process it becomespossible for a fibre manufacturer to supply filaments and fibres whichhave been dyed uniformly in a wide range of colours and shades and whichmay be stabilised e.g. by means of a crimp setting process, so that thefinal product maintains its tenacity and elongation and does not shrink,or shrinks e.g. less than 1% in boiling water, depending on thestabilising treatment. As far as we are aware, all commerciallyavailable synthetic and particularly polyester staple fibres shrink afurther amount during any subsequent commercial high temperature dyeingtreatment, which is usually carried out on fabrics with a loss intenacity and an increase in elongation. In contradistinction our dyedfibres obviously do not require dying but in their stabilised condition,in fabric form, they do not shrink. Thus using our dyed filaments andfibres which have been stabilised, it is possible to make the requireddesign and colour in fabrics which do not require any further dyeingtreatment and therefore do not shrink, moreover the original tenacityand elongation of the fibre is maintained.

Although the foregoing description relates to filaments and fibres, webelieve the process to be applicable also to undrawn monofilaments,films and similarly shaped objects.

What we claim is:

1. A rapid continuous integrated process for coloring filaments meltspun from synthetic linear polymers selected from the group consistingof linear polyesters, copolyesters of the polyethylenesebacate/terephthalate type, polyamides and polyolefins consistingessentially of applying a dye dissolved in at least one hotsubstantially non-aqueous solvent to undrawn filaments having abirefringence of less than 10 10 melt spun from synthetic linearpolymers under conditions such that after immersion times of up to 30seconds penetration of dye into the filaments is at least 60%, drawingthe filaments at least three times their length and heating thefilaments, said dye consisting essentially of finely divided acetate dyeand said solvent being selected from the group consisting of ethyleneglycol, diethylene glycol, polyethylene glycols having an averagemolecular weight of 200-6000, their esters and ethers, dimethylsebacate, diethyl sebacate, oleic acid, Inesitylene, triphenylphosphite, glycerol and mixtures thereof which are soluble andcompatible with each other and which are liquid under the treatingconditions.

2. The process of claim 1 wherein said polymer is polyethyleneterephthalate and the dye is a disperse acetate dye dissolved in anethylene glycol, the dye solution is applied by immersing the filamentstherein at a temperature between 100 C. and 150 C. with an immersiontime of 5-15 seconds; the amount of dye solution pick-up is in the rangeof 25-35%; the concentration of dye in the filaments and in the solventis where C, is the concentration of the dye in the filaments and has avalue of at least 2, C is the concentration of the dye in the solventand this does not exceed saturation and K has a value of 0.2-1.6.

3. The process of claim 2 wherein the filaments are heated in steam atto C. while drawing and then subsequently washed at 60 to 70 C. toremove excess dye and solvent, followed by drying and heat-setting.

References Cited by the Examiner UNITED STATES PATENTS 2,278,888 4/ 1942Lewis.

2,545,075 3/1951 Dungler 68-99 2,577,846 12/1951 Feild 8-17 2,878,7783/1959 Kusters 68-99 3,012,842 12/1961 Aeberhardt et al. 8-55 3,046,0767/1962 Upshur 8-55 3,069,218 12/1962 Hermes 264-78 3,073,663 1/1963Rosener 8-55 OTHER REFERENCES Marvin: J.S.D.C., 70, January 1954, pp.16-21, particularly pp. 1, l8 and 19.

The Textile Manufacturer, December 1949, pp. 590- 591.

Vickerstaif: The Physical Chemistry of Dyeing, 2nd ed., 1954,Interscience Publishers Inc., New York, pp. 439, 440, 442, 458-461 and489-492.

Waters: J.S.D.C., vol. 66, No. 12, December 1950, pp. 609-613,particularly pp. 610 and 612 NORMAN G. TORCHIN, Primary Examiner.

MORRIS O. WOLK, Examiner.

1. A RAPID CONTINUOUS INTGEGRATED PROCESS FOR COLORING FILAMENTS MELTSPUN FROM SYNTHETIC LINEAR POLYMERS SELECTED FROM THE GROUP CONSISTINGOF LINEAR POLYESTERS, COPOLYESTERS OF THE POLYETHYLENESEBACATE/TEREPHTHALATE TYPE, POLYAMIDES AND POLYOLEFINS CONSISTINGESSENTIALLY OF APPLYING A DYE DISSOLVED IN AT LEAST ONE HOTSUBSTANTIALLY NON-AQUEOUS SOLVENT TO UNDRAWN FILAMENTS HAVING ABRIEFRINGENCE OF LESS THAN 10X10-3 MELT SPUN FROM SYNTHETIC LINEARPOLYMERS UNDER CONDITINS SUCH THAT AFTER IMMERSION TIMES OF UP TO 30SECONDS PENETRATION OF DYE INTO THE FILAMENTS IS AT LEAST 60%, DRAWINGTHE FILAMENTS AT LEAST THREE TIMES THEIR LENGTH AND HEATING THEFILAMENTS, SAID DYE CONSISTING ESSENTIALLY OF FINELY DIVIDED ACETATE DYEAND SAID SOLVENT BEING SELECTED FROM THE GROUP CONSISTING OF ETHYLENEGLYCOL, DIETHYLENE GLYCOL, POLYETHYLENE GLYCOLS HAVING AN AVERAGEMOLECULAR WEIGHT OF 200-6000, THEIR ESTERS AND ETHERS, DIMETHYLSEBACATE, DIETHYL SEBACATE,OLEIC ACID, MESITYLENE, TRIPHENYL PHOSPHITE,GYCEROL AND MIXTURES THEREOF WHICH ARE SOLUBLE AND COMPATIBLE WITH EACHOTHER AND WHICH ARE LIQUID UNDER THE TREATING CONDITION.